n = int(input())
c = input()

w = c.count("W")
r = c.count("R")

ans = 0
for i in range(r):
  if c[i] == "W": ans += 1
print(ans) n = int(input()) n int(input()) int input() input c = input() c input() input w = c.count("W") w c.count("W") c.count c count "W" r = c.count("R") r c.count("R") c.count c count "R" ans = 0 ans 0 for i in range(r):
  if c[i] == "W": ans += 1 i range(r) range r if c[i] == "W": ans += c[i] == "W" c[i] c i "W" print(ans) print ans n = int(input()) int(input()) n r = c.count("R") c.count("R") r w = c.count("W") c.count("W") w ans = 0 0 ans c = input() input() c
n = int(input())
c = input()

w = c.count("W")
r = c.count("R")

ans = 0
for i in range(r):
  if c[i] == "W": ans += 1
print(ans)